If used in conjunction with punctual blood samples and evaluation of clinical signs, urine sampling can be a valuable monitoring tool. Urine only tests positive for glucose if the blood glucose concentration remains above the renal threshold for a substantial period of time. This occurs when glycemia reaches 200-280 mg/dL (11.1-15.6 mmol/L) in the cat.
Urine monitoring is also a quick and easy method of detecting ketonuria and hence a potential emergency. See diabetic ketoacidosis for more information. However, when you need to adjust a pet’s insulin dose, evaluate glycemia by performing a glucose curve.
Pet owners can use 2 protocols to test urine:
1. Have the pet owner test urine 3 times a day: before the first meal (test 1), before the second meal (test 2), and late in the evening (test 3). (No change in feeding schedule is required for cats fed ad libitum.)
Refer to the following table:
|TEST 1||TEST 2||TEST 3||Action recommended|
|Trace||–||Trace||Duration of Vetsulin activity may be a little too short. Perform glucose curve.|
|+||–||+||Potential Somogyi effect. Perform glucose curve.|
|+||+||+||Dose potentially too low. Perform glucose curve.|
|–||–||–||Dose potentially too high. Perform glucose curve.|
2. Ask the pet owner to closely monitor a 24-hour period by collecting as many urine samples as possible. A persistent glycosuria will indicate the need for a complete re-evaluation and glucose curve.
There are special litter crystals available that can be added to the litter and change color to indicate the cat's urine glucose levels. Urine collection can also be facilitated by using special cat litter, such as hydrophobic sand.